• Asian-Australasian Journal of Animal Sciences
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• v.19 no.11
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• pp.1617-1622
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• 2006

Long-term storage of feeds or feedstuffs in high temperature and humid conditions can be difficult because of microbial contamination. Essential oil isolated from industrial waste citrus peel could be used as a preservative because it is likely to have anti-bacterial and anti-fungal activity. Our objective was to determine whether different levels (0.028, 0.056 and 0.112 g/kg) of citrus essential oil (CEO) would provide anti-microbial activity and enhance preservation of animal feed without influencing rumen fermentation. At 0.112 g/kg, CEO inhibited growth of Escherichia coli (ATCC 25922) and Salmonela enteritidis (IFO 3313). Growth of E. coli recovered after 24 h of incubation, but S. enteritidis continued to be inhibited for 72 h. Preservation of antibiotic-free diets for swine was assessed by observing anti-aflatoxin activity. Aflatoxin was detected in control feed samples on days 16 (8 ppb) and 21 (8 ppb) and in anti-fungal agent (AA) treated samples on days 16 (2 ppb) and 21 (4 ppb). However, aflatoxin was not detected in feed samples treated with CEO. Treatment with CEO and AA did not influence ruminal pH, dry matter digestibility (DMD) or organic matter digestibility (OMD) over 48 h of incubation in rumen fluid. Acetate and propionate were slightly higher with CEO treatment (p<0.05), but total concentration of volatile fatty acid (VFA) was not significantly affected by treatment. Ammonia-N concentration was slightly higher for the control treatment (p<0.05). This study showed that treating feed with CEO enhances preservation of animal feed without influencing in vitro rumen fermentation.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.6
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• pp.804-810
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• 2017

Objective: The objective of this study was to evaluate the effect of sodium diacetate (SDA) on fermentation profile, chemical composition and aerobic stability of alfalfa (Medicago sativa L.) silage. Methods: Fresh alfalfa was ensiled with various concentrations of SDA (0, 3, 5, 7, and 9 g/kg of fresh forage). After 60 days of the ensiling, the samples were collected to examine the fermentative quality, chemical composition and aerobic stability. Results: The application of SDA significantly (p<0.05) decreased silage pH with the lowest value in silage with 7 g/kg of SDA. The proliferations of enterobacteria, yeasts, molds and clostridia were inhibited by SDA, resulted in lower ethanol, propionic and butyric acid concentrations and dry matter loss in SDA treated silages than control. The increasing SDA linearly decreased free amino acid N (p<0.001), ammonia N (p = 0.018) and non-protein N (p<0.001), while linearly increased water soluble carbohydrate (p<0.001) and peptide N (p<0.001). It is speculated that SDA accelerated the shift from homofermentative to heterofermentative lactic acid bacteria during the silage fermentation, indicated by lower lactic acid production in SDA-9 than SDA-7 silages after 60 days of ensiling. Alfalfa silages treated with SDA at 7 g/kg had highest Flieg's point and remained stable more than 9 d during aerobic exposure under humid and hot conditions in southern China. Conclusion: SDA may be used as an additive for alfalfa silages at a level of 7 g/kg.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.9
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• pp.1278-1284
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• 2017

Objective: To assess the potency of calcium propionate (CAP) used as silage additive, an experiment was carried out to evaluate the effect of CAP on the nitrogen transformation, fermentation quality and aerobic stability of alfalfa silages. Methods: Alfalfa was ensiled with four levels of CAP (5, 10, 15, and 20 g/kg of fresh weight [FW]) in laboratory silos for 30 days. After opening, the silages were analyzed for the chemical and microbiological characteristics, and subjected to an aerobic stability test. Results: The increasing proportion of CAP did not affect pH, lactic acid (LA) concentrations and yeast counts, while linearly decreased counts of enterobacteria (p = 0.029), molds (p<0.001) and clostridia (p<0.001), and concentrations of acetic acid (p<0.001), propionic acid (p<0.001), butyric acid (p<0.001), and ethanol (p = 0.007), and quadratically (p = 0.001) increased lactic acid bacteria counts. With increasing the proportion of CAP, the dry matter (DM) loss (p<0.001), free amino acid N (p<0.001), ammonia N (p = 0.004), and non-protein N (p<0.001) contents were linearly reduced, whereas DM (p = 0.048), water soluble carbohydrate (p<0.001) and peptide N (p<0.001) contents were linearly increased. The highest Flieg's point was found in CAP10 (75.9), represented the best fermentation quality. All silages treated with CAP improved aerobic stability as indicated by increased stable hours compared with control. Conclusion: The addition of CAP can suppress the undesirable microorganisms during ensiling and exposure to air, thereby improving the fermentation quality and aerobic stability as well as retarding the proteolysis of alfalfa silage. It is suggested that CAP used as an additive is recommended at a level of 10 g/kg FW.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.1
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• pp.139-147
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• 1999

Peptides are formed in the rumen as the result of microbial proteinase activity. The predominant type of activity is cysteine ptoteinase, but others, such as serine proteinases, are also present. Many species of protozoa, bacteria and fungi are involved in ptoteolysis; large animal-to-animal variability is found when proteinase activities in different animals are compared. The peptides formed from proteolysis are broken down to amino acids by peptidases. Different peptides are broken down at different rates, depending on their chemical composition and particularly their N-terminal structure. Indeed, chemical addition to the N-terminus of small peptides, such as by acetylation, causes the peptides to become stable to breakdown by the rumen microbial population; the microorganisms do not appear to adapt to hydrolyse acetylated peptides even after several weeks exposure to dietary acetylated peptides, and the amino acids present in acetylated peptides are absorbed from the small intestine. The amino acids present in some acetylated peptides remain available in nutritional trials with rats, but the nutritive value of the whole amino acid mixture is decreased by acetylation. The genus Prevotella is responsible for most of the catabolic peptidase activity in the rumen, via its dipeptidyl peptidase activities, which release dipeptides rather than free amino acids from the N-terminus of oligopeptides. Studies with dipeptidyl peptidase mutants of Prevotella suggest that it may be possible to slow the rate of peptide hydrolysis by the mixed rumen microbial population by inhibiting dipeptidyl peptidase activity of Prevotella or the rate of peptide uptake by this genus. Peptides and amino acids also stimulate the growth of rumen microorganisms, and are necessary for optimal growth rates of many species growing on tapidly fermented substrates; in rich medium, most bacteria use pre-formed amino acids for more than 90% of their amino acid requirements. Cellulolytic species are exceptional in this respect, but they still incorporate about half of their cell N from pre-formed amino acids in rich medium. However, the extent to which bacteria use ammonia vs. peptides and amino acids for protein synthesis also depends on the concentrations of each, such that preformed amino acids and peptides are probably used to a much lesser extent in vivo than many in vitro experiments might suggest.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.10
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• pp.639-647
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• 2017

This basic study is focused on the physically removal method of carbon dioxide from the decomposition of ammonium carbarmate to prevent the recombination of ammonium salts. A basic visual experimental set-up was designed and constructed to observe the recombination phenomena from the proper composition of ammonia gas, carbon dioxide gas, and compressed air dilution gas. To quantify the recombination phenomena, a simple device was designed to measure the weight change under severe cases for three different tube sizes. The temperature and pressure in the visual tube and the volumetric flow rates of the nitrogen dilution gas were studied and the conditions to avoid recombination were analyzed according to mean free path theory. Diffusivity values based on the Chapman-Enskog theory were calculated from the experimental data. These value may serve as an index for the prevention of recombination.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.414-420
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• 2006

Effluent from an anaerobic digestion system with an elutriated phased treatment(ADEPT, Anaeorbic Digestion Elutriated Phase Treatment) for piggery waste treatment using anaerobic ammonium oxidation(ANAMMOX) process was used as a substrate of partial nitrification reactor. In mesophilic condition($35^{\circ}C$), controlling parameters of nitrite accumulation were HRT, pH, free ammonia(FA) and hydroxylamine rather than dissolved oxygen. Bicarbonate alkalinity consumption ratio including bicarbonate stripping and buffering was 8.78 g $Alk._{comsumed}/g\;NH_4-N_{converted}$. In steady state for 1 day of HRT and $2.7{\sim}4.4mg/L$ of DO, $NO_2-N/NH_4-N$ ratio of partial nitrification effluent was about $1{\sim}3$, which was applicable to ANAMMOX reactor influent for the combined partial nitrification-ANAMMOX process.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.3
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• pp.191-197
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• 1992

In order to investigate the chemical components of acid precipitation at Kangwha near the Yellow Sea and Seoul in Korea, the precipitation samples were collected by wetonly precipitation sampler from February 1991 to January 1992, and pH, electric conductivity(E. C.) and major water-soluble ionic components were analyzed. Strong negative linear correlations were observed between the rainfall amount and the sum of major ionic components in $\mu eq/\ell$ at two sites. The sum of major ionic components also correlated negatively with rain intensity. The analytical results of precipitation samples at two sites were compared each other. Average values of volume-weighted pH were found to be 5.21 at Kangwha and 5.09 at Seoul. The cationic abundance($\mu eq/\ell$) in rainwater showed the general trend $NH_4^+ > Na^+ > Ca^{2+} > Mg^{2-+} > H^+ > K^+$ at Kangwah and $NH_4^+ > Ca^{2+} > Na^+ > H^+ > Mg^{2+} > K^+$ at Seoul. The anionic abundance showed the general trend $SO_4^{2-} > Cl^- > NO_3^-$ at Kangwha and $SO_4^{2-} > NO_3^- > Cl^-$ at Seoul. The concentrations of seasalt such as $Na^+ and Cl^-$ were higher at Kangwha than Seoul. The concentrations of $nss-SO_4^{2-}, nss-Cl^- and NO_3^-$ which are acid composition were higher at Seoul(96.3 $\mu eq/\ell$) than Kangwha(69.0 $\mu eq/\ell$). The contribution of seasalt to the composition of precipitation were higher at Kangwha(34.1%) than Seoul(15.7%). Ammonia and calcium species in rainwater at Kangwha and Seoul are interpreted to have 91% of neutralizing capacity of the original sulfuric and nitric acids. Provided that the precipitation acidity originates primarily from sulfate and nitrate, sulfate was found to contribute about 73-75% of the free precipitation acidity.

• Microbiology and Biotechnology Letters
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• v.14 no.5
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• pp.427-432
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• 1986

The regulation of three ammonia assimilatory enzymes, GDH (glutamate dehydrogenase), GS (glutamine synthetase) and GOGAT (glutamate synthase), has been examined in C. glutamicum. Three kinds of arginine auxotrophs blocked in each step of arginine biosynthetic pathway from glutamate were selected as arg 5, arg 6, arg 8. Histidine and tryptophan auxotrophs were also selected because histidine and tryptophan repressed GS biosynthesis in E. coli. These strains were cultured on the media containing nitrogen-excess and limited conditions, to compare the specific activities of ${\alpha}$-ketoglutarate dehydrogenase(${\alpha}-KGDH$), GDH, GS, GOGAT from the cell-free extracts. These results showed that enzyme levels of ${\alpha}-KGDH$ and GDH from 3 kinds of arginine auxotrophs, histidine and tryptophan auxotrophs in nitrogen-excess condition and those of GS and GOGAT in nitrogen limited condition were increased compared with opposite condition. The tryptophan and histidine auxotrophs showed higher level of glutamate and glutamine than parental strains and other mutants. it is assumed that the higher levels of ${\alpha-KGDH}$ and GDH from mutants in nitrogen-excess condition promoted the accumulation of glutamate and glutamine in fermentation broth. The inhibition of GS activities by ADP suggested that GS is regulated by energy charge in C. glutamicum. The results with histidine, tryptophan, glycine, alanine, serine and GMP implied that a system of feedback inhibition were effective. The GDH, GS and GOGAT biosynthesis in culture broth was markedly repressed by the nature and kinds of available nitrogen sources such as tryptophan, proline, glycine, alanine, serine and tyrosine.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.636-641
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• 2007

A pilot-scale biofilm nitiritation reactor was operated with the reject water from a large wastewater treatment plant. The effects of various operating parameters including pH, temperature, dissolved oxygen, solids and organic concentrations were examined. A stable nitritation was achieved at operating pH range of 7.3 to 8.8 with an alkalinity addition. Higher operating temperature of $35{\pm}0.7^{\circ}C$ achieved more stable nitritation compared to $30{\pm}0.2^{\circ}C$. It has been noticed that nitrite accumulation maintained with DO, solids and organic concentrations range of 0.8 to 3.9 mg/L, 3,400 to 11,000 mg/L, and 86 to 572 mg/L, respectively. It seems that the accumulation of nitrite was caused by both the inhibition of $NO_2{^-}$ oxidizers due to free ammonia and the maintenance of the high operating temperature of $35^{\circ}C$ which promote to accumulate the $NH_4{^+}$ oxidizers in the reactor. According to microbial community analysis of fluorescence in situ hybridization and INT-Dehydrogenase measurements, more nitrifiers were presented in attached form compared to suspended growth.

• Journal of the Korean Vacuum Society
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• v.19 no.1
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• pp.58-65
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• 2010

AlN thin films were deposited on sapphire substrates and ZnO templates by rf-magnetron sputtering. Powder-sintered AlN target was adopted for source material. Thickness of AlN layer was linearly dependent on plasma power from 50 to 110 W, and it decreased slightly when working pressure increased from 3 to 10 mTorr due to short mean free path of source material sputtered from AlN target by Ar working gas. When $N_2$ gas was mixed with Ar, the thickness of AlN layer decreased significantly because of low sputter yield of nitrogen. AlN layer was also deposited on ZnO template. However, it showed weak thermal stability that the interface between AlN and ZnO was deteriorated by rapid thermal annealing treatment above $700^{\circ}C$. In addition, ZnO layer was largely attacked by MOCVD ambient gas of hydrogen and ammonia around $700^{\circ}C$ through inferior AlN layer deposited by sputtering. And AlN layers were fully peeled off above $900^{\circ}C$.